
function nodet(a:number,b:number):number
function nodet(a:string,b:string):string
function nodet(a:number|string,b:number|string):number|string{
    if(typeof a === 'number' && typeof b === 'number'){
        return a*b
    }else  if(typeof a === 'string' && typeof b === 'string'){
        return a+b
    }
    throw new Error('a|b not anumber|string')
}
let s = nodet(1,2)

function fn(a:number,b:string='2'){}